Example
add2 - adds the numbers in registers $4 and $5 and puts the result in $6
addi $4,$0,10 #$4 = 10
addi $5,$0,20 #$5 = 20
jal add2 #call add2
add $4,$0,$6
addi $5,$0,25
jal add2
sw $6, X($20) #stores result
add2 : add $6,$4,$5 #procedure body
jr $31 #return